I would recommend against the options 2 and 3 you mentioned - for 2 because I wouldn't place any special "test mode" code into the main module, since you end up testing something different from the code that the user actually ends up running. Adding a test library has the least issues IMO, the only thing to keep in mind is that if it contains complex functions, those should be tested as well, which it's fine to do as part of the test suite. Have a look at the t folder in any of my distros, https://metacpan.org/author/HAUKEX - although I admit I figured some of it out myself, so I'm not saying everything I did there is a best practice :-)

Update: Dependencies for tests are specified via TEST_REQUIRES in Makefile.PL.

Update 2: Regarding "hide from CPAN indexer", see e.g. https://www.effectiveperlprogramming.com/2012/04/hide-namespaces-from-pause/

In reply to Re: code duplicate in tests -- code or custom module only needed to test by haukex
in thread code duplicate in tests -- code or custom module only needed to test by Discipulus

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